1. Field of the Invention
The present invention relates to a test apparatus for printed circuit board and an assembly kit therefor. More particularly, it relates to a type of test apparatus which utilizes probes to detect that electrical contacts are established.
2. Background
It is known to use a test apparatus shown in FIG. 4 for testing for a disconnection in a printed circuit pattern of a printed circuit board, a short in the printed circuit patterns, and for defects, etc. of electronic parts mounted on a printed circuit board. FIG. 4 shows a test apparatus which is testing a printed circuit board.
Referring to FIG. 4, a conventional apparatus is described herein. A test unit 400 including an interface plate 401 and a socket retention plate 402 is vertically moved by driving means (not shown). While the test unit is in a raised state, a printed circuit board 403 to be tested is mounted on a printed circuit board setting plate 404, and thereafter the test unit 400 is lowered so that a probe 407 comes in contact with and tests the printed circuit board 403.
A socket 406 is fixed on the socket retention plate 402. The first probe 407 and a second probe 405 are inserted into the socket. The first probe 407 comes in contact with a printed circuit pattern 409 on the printed circuit board 403, and the second probe 405 comes in contact with a pad 408 provided on the interface plate 401. On the outer circumference of the socket 406, an annular protrusion is provided, and by driving the socket 406 into the socket retention plate 402 by using a tool provided for that purpose, the socket 406 is pressfit.
The socket retention plate 402 and the interface plate 401 are connected by a support column 420. The length of the support column 402 is designed so that the second probe 405 comes into contact with the interface board 401 with a predetermined amount of pin pressure.
The interface plate 401 is a printed circuit board, and connects the pad 408, with which the second probe 405 make a contact, and the lead of a connector A 411 by a printed circuit pattern. Accordingly, the printed circuit pattern of the printed circuit board 403 to be tested and the tester are connected via the first probe 407, the socket 406, the second probe 405, the printed circuit pattern of the interface plate 401, the connector A 411, a connector B 412 and a cable 413, and electrical signals are provided from the tester to a certain location on the interface plate 401, thereby testing the printed circuit board 403 by observing electric signals at a predetermined location on the interface board 401.
However, there are problems with the conventional technology as described below. First, two materials are used for the probes 407, 405 and the socket 406. For this reason, the material cost is high and the number of assembly steps are increased. Further, in order to press-fit the probes 407, 405, a predetermined amount of play must exist between the outer diameters of the probes 407, 405 and the interior diameter of the socket 406, and this results in inaccuracies in the locations of the tip ends of the probes 407, 405.
Second, in order to increase the accuracy in the locations of the tip ends of the probes 407, 405, it is necessary to increase the degree of perpendicularity of the socket 406 with respect to the socket retention plate 402. In order to achieve this, it is necessary to thicken the socket retention plate 402, but if it is thickened, the test unit 400 becomes heavy.
Third, there are times when flux which is generated during soldering becomes attached to the printed circuit board 403, and in order to eliminate contact defects between the probes 407, 405 and the printed circuit board 403 to be tested, it is necessary to place a predetermined amount of load on the printed circuit board 403 with the probes 407, 405. At that time, if there are numerous probes 407, 405, this place a significant amount of load on the socket retention plate 402, and it becomes necessary to thicken the socket retention plate 402. However, this causes the test unit 400 to be heavy.
Fourth, a high level of skills are required to accurately drive a great number of sockets into the socket retention plate 402. Accordingly, only after all the sockets 406 and the probes 407, 405 are assembled onto the test unit 400, the test unit 400 is shipped to a user from the test apparatus manufacturer. For this reason, a special packaging is required in order to protect the tip ends of the probes 407, 405, and further because assembled products are shipped, there is a problem of large package size. It is therefore an object of the present invention to provide a probe which can be used without a socket.
It is therefore another object of the present invention to decrease the number of parts which are required.
It is yet another object of the present invention to decrease the material cost.
It is another object of the present invention to provide an assembly kit for a test apparatus which even a user can use to accurately test a printed board.
Additional objects and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment thereof, which proceeds with reference to the accompanying drawings.